In today's generation of semiconductor chips, there are up to 5000 fuses per chip with as many as 1000-4000 deletes per second required to make laser blow technology economically feasible. In future chips, the number of fuses per chip may grow even higher, e.g. 50,000 or more.
In conventional fusing, either laser delete of the metal conductors or electrically blowing the polysilicon fuse links is employed. Both of these existing technologies involve relatively large amounts of energy to superheat and delete the fuse. Such prior art methods are detrimental to the integrity of low dielectric constant materials, particularly foam type materials, thus limiting their use as interlayer dielectric films.
Because of line to line coupling which slows signal propagation, there is a trend for the interlevel dielectric to be composed of a low dielectric constant material such as a polyimide nanofoam or a porous glass such as zero gel. The low dielectric constant materials are not solids and thus they will collapse when their thermal budget or glass transition temperature, Tg, (about 300.degree. C.) or mechanical strength is exceeded. Moreover, to improve signal propagation in semiconductor chips, high conductance materials such as copper are now being used as the conductive material.
There are two problems associated with using the above materials. First, conventional laser blowing (or even electric blowing) will damage the low dielectric constant material causing it to collapse, changing its dielectric constant and integrity. When copper or another suitable high conductance material is used, particles of the high conductance material may be released into the pores of the low dielectric constant material. This release may cause a potential reliability problem which could compromise the performance of the basic local structure of the semiconductor chip.
In view of the drawbacks with prior art blowing methods, there is a need for developing a new and improved semiconductor fuse structure which contains a fuse that causes little or no damage to the surrounding structure when the fuse is deleted. The fuse must also offer the opportunity for denser fuse layouts and the capability of providing a higher number of fuses in the semiconductor structure. Any new fuse structure must be able to use low dielectric constant materials as well as high conductance materials, e.g. Cu.